1. Field of the Invention
The present invention relates to methods of dealing with excessive vibration in a hard disk drive.
2. Background of the Related Art
Computer systems use hard disk drives to provide large amounts of data storage. The performance of hard disk drives has increased to the point that consumers can buy a low cost hard disk drive (HDD) with 2 terabytes (TB) of data storage for less than one hundred dollars. As a result, some enterprises are implementing these low cost HDDs instead of the more robust and expensive enterprise HDDs previously used.
Unfortunately, these low cost HDDs are very sensitive to transient vibration events, such as an earthquake or a gas fire suppression release in a data center. This puts critical data at risk. Furthermore, the vibration and acoustic sensitivity of these HDDs is expected to increase along with the data storage capacity. For example, a 4 TB HDD is expected to exhibit twice the vibration and acoustic sensitivity as a 2 TB HDD of the same design.
When a hard disk drive experiences a high level of external vibration and cannot respond to a data request, a host bus adapter or controller will complete an error recovery process and wait for a reply until a time out value is reached. If the HDD has not replied by the end of the time out period, then the host bus adapter or controller identifies the HDD as “failed” and writes that information to a metadata log stored on the HDD unit. After that, this metadata will prevent a host bus adapter or controller from using the “failed” HDD. Rather, a user must buy a new HDD and load it with data recovered in some manner or obtained from a backup copy. This is a slow process with high risk of data loss.
A redundant array of inexpensive disks (RAID) is one way to protect data from being lost when a HDD fails. One advantage of a RAID array is that if one of the HDDs in the array fails, the data array can be reconstructed from the remaining HDDs in the array. Unfortunately, vibration from some environmental events, such as earthquakes, fire suppression system deployment, and vehicular traffic, can affect all of the HDDs in the array or even all of the HDDs in the data center. Depending upon the design of the array, simultaneous failure of multiple HDDs may prevent the array from being reconstructed from data on the remaining HDDs. Rather, the failed HDDs must be replaced and the data array must be rebuilt from scratch from a backup copy of the data on a new set of HDDs. This process may result in permanent data loss, temporary unavailability of data storage capacity, and significant capital and operational expense.